This application is related to a co-pending application that bears U.S. Pat. No. 5,940,319, entitled "MAGNETIC RANDOM ACCESS MEMORY AND FABRICATING METHOD THEREOF," filed on Aug. 31, 1998, assigned to the same assignee and incorporated herein by this reference, co-pending application that bears U.S. Pat. No. 6,024,885, entitled "PROCESS OF PATTERNING MAGNETIC FILMS" filed on Dec. 8, 1997, assigned to the same assignee and incorporated herein by this reference and issued U.S. Pat. No. 5,768,181, entitled "MAGNETIC DEVICE HAVING MULTI-LAYER WITH INSULATING AND CONDUCTIVE LAYERS", issued Jun. 16, 1998, assigned to the same assignee and incorporated herein by this reference.
Typically, a magnetic element, such as a magnetic memory element, has a structure that includes ferromagnetic layers separated by a non-magnetic layer. Information is stored as directions of magnetization vectors in magnetic layers. Magnetic vectors in one magnetic layer, for instance, are magnetically fixed or pinned, while the magnetization direction of the other magnetic layer is free to switch between the same and opposite directions that are called "Parallel" and "Antiparallel" states, respectively. In response to Parallel and Antiparallel states, the magnetic memory element represents two different resistances. The resistance has minimum and maximum values when the magnetization vectors of the two magnetic layers point in substantially the same and opposite directions, respectively. Accordingly, a detection of changes in resistance allows a device, such as an MRAM device, to provide information stored in the magnetic memory element. The difference between the minimum and maximum resistance values, divided by the minimum resistance is known as the magnetoresistance ratio (MR).
An MRAM device integrates magnetic elements, more particularly magnetic memory elements, and other circuits, for example, a control circuit for magnetic memory elements, comparators for detecting states in a magnetic memory element, input/output circuits, etc. These circuits are fabricated in the process of CMOS (complementary metal-oxide semiconductor) technology in order to lower the power consumption of the device.
In addition, magnetic elements structurally include very thin layers, some of which are tens of angstroms thick. The performance of the magnetic element is sensitive to the surface conditions on which the magnetic layers are deposited. Accordingly, it is necessary to make a flat surface to prevent the characteristics of a magnetic element from degrading.
During typical magnetic element fabrication, such as MRAM element fabrication, which includes metal films grown by sputter deposition, evaporation, or epitaxy techniques, the film surfaces are not absolutely flat but instead exhibit surface or interface waviness. This waviness of the surfaces and/or interfaces of the ferromagnetic layers is the cause of magnetic coupling between the free ferromagnetic layer and the other ferromagnetic layers, such as the fixed layer or pinned layer, which is known as topological coupling or Neel's orange peel coupling. Such coupling is typically undesirable in magnetic elements because it creates an offset in the response of the free layer to an external magnetic field.
The ferromagnetic coupling strength is proportional to surface magnetic charge density and is defined as the inverse of an exponential of the interlayer thickness. As disclosed in U.S. Pat. No. 5,764,567, issued Jun. 9, 1998, and entitled "MAGNETIC TUNNEL JUNCTION DEVICE WITH NONFERROMAGNETIC INTERFACE LAYER FOR IMPROVED MAGNETIC FIELD RESPONSE", by adding a non-magnetic copper layer next to the aluminum oxide tunnel barrier in a magnetic tunnel junction structure, hence increasing the separation between the magnetic layers, reduced ferromagnetic orange peel coupling, or topological coupling, is achieved. However, the addition of the copper layer will lower the MR of the tunnel junction, and thus degrade device performance. In addition, the inclusion of the copper layer will increase the complexity for etching the material.
Accordingly, it is a purpose of the present invention to provide an improved magnetic element with improved field response.
It is another purpose of the present invention to provide an improved magnetic element that includes reduced ferromagnetic coupling, more particularly ferromagnetic coupling of topological origin.
It is a still further purpose of the present invention to provide a method of forming a magnetic element with improved field response.
It is still a further purpose of the present invention to provide a method of forming a magnetic element with improved field response which is amenable to high throughput manufacturing.